Immersed outlet for casting metal

ABSTRACT

The invention is directed to an immersion nozzle for casting metal, especially steel, in plants for the continuous casting of thin slabs. On order to provide an immersion casting pipe that is easy to manufacture, has a long life, and enables the liquid metal to flow out in a uniform manner, it is suggested, according to the invention, that the pour-in part (11) is a pipe having a straight-surface front mouth (12), and the pour-out part (21) is constructed from plane-surface wall elements (22, 23). For this purpose, the circular cross-sectional area (A R ) of the pour-in part (11) is in a relationship to the rectangular free cross-sectional area (A E ) of the pour-out part (21) such that A R  /A E  ≧1.7.

FIELD OF THE PRESENT INVENTION

The present invention is directed to an immersed outlet (also referredto as an immersion casting pipe or an immersion nozzle) for castingmetal, especially steel, in plants for the continuous casting of thinslabs, with a pour-in part which is fastened at a pour-in or castingvessel and which has a circular cross section, and with a pour-out partwhich dips into the melt located in a rectangular mold, the mouth of thepour-out part being rectangular in cross section.

BACKGROUND OF THE INVENTION

An immersion nozzle, especially for casting thin slabs, is known from EP0 630 712. This immersion nozzle is divided into two portion, and thelength of its lower shaped brick is substantially greater than itswidth. The individual portions are formed by separate shaped bricks,wherein the shaped bricks engage in one another at their ends which faceone another and a seal is arranged between the meshing ends of theshaped bricks.

The individual shaped bricks have a complicated shaped construction withdistinct differences in wall thickness.

DE 37 09 188 A1 likewise discloses a pour-out pipe for metallurgicalvessels. The upper longitudinal portion of the pour-out pipe is round incross section and its lower longitudinal portion is rectangular in crosssection. The dimensions in the mouth region have a length-to-width ratioof 20:1 to 80:1. The outlet of the immersion casting pipe is formed bytwo mouth openings which together have a flow cross section which is notquite as large as the flow cross section at the stopper end.

A ratio of less than 1:1 between the flow cross section in the inletpipe and at the outlet of the immersion casting pipe is achieved by flowdeflection and by narrowing two mouth openings.

SUMMARY OF THE INVENTION

The object of the invention is to provide an immersion nozzle which iseasy to manufacture, has a long life, has a construction which isresistant to thermal stresses with respect to manufacture and operation,and enables the liquid metal to flow out in a uniform manner.

The immersion nozzle is constructed from two basic structural componentparts, namely a tubular pour-in part and a rectilinear orstraight-surface pour-out part. Provided between these two basicstructural component parts, which are completely different from oneanother with respect to shape, is a transition of short overall length.

Surprisingly, transition has virtually no effect on the flow behavior ofthe liquid steel flowing through the immersion nozzle insofar as thepour-out part is formed from plane-surface wall elements and has a freecross-sectional area which is less than half of the cross-sectional areaof the pour-in part.

Regardless of the shape of the transition from the tubular pour-in partto the rectangular pour-out part, the flow of molten steel can beconducted so as to be completely calm insofar as the plane-surface wallelements are arranged virtually parallel to one another.

As a result of the simple shaped elements which are, specifically,either round or rectilinear, the individual structural component partsof the immersion nozzle are adapted to the anticipated high thermalstresses. In addition to the simple geometrical shape, wall elements ofidentical thickness are used.

Since the transition between the pour-in part and the pour-out part isof secondary importance to the flow ratios, constructional freedom canbe exploited for purposes of optimization with respect to freeing thetransition part from stresses.

A positive influence can be exercised on the flow ratios especially inthe transition region by baffle or deflector elements arranged at thebase of the pour-in part.

The complete calming of the flow behavior in the melt which is achievedby the simple shape of the pour-out part enables the required throughputquantities to be produced in the casting of thin slabs while minimizingthe free outlet area.

The requirement for small surface area makes it possible to useimmersion nozzles for thin-slab molds with parallel side walls and awidth of up to 60 mm.

Owing to the identical shaping of the mouth of the immersion nozzle andthe inlet of the mold, a constant free surface of the level of the meltlocated in the mold adjusts to the dimensions of the mold.

Due to the calmed, uniform guiding of the melt in the pour-out part ofthe immersion nozzle and the similarly shaped pour-out part and moldhaving only slight differences between them with respect to theircross-sectional area, the melt is guided in the mold with littlewhirling. The melt is adjusted with respect to amount via an adjustingmember in the casting vessel, normally via a stopper end.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a basic diagram of the immersion nozzle and the castingvessel;

FIG. 2 shows an immersion nozzle with a spreading of the immersioncasting part at the head end;

FIG. 3 shows another embodiment of the immersion nozzle of FIG. 1 with aroof-shaped pour-out part;

FIG. 4 shows the detail of the transition between the pour-in part andpour-out part;

FIG. 5 shows the arrangement of the pour-in part and pour-out part atthe casting vessel.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 shows a section of a casting vessel 41 with the outlet opening 43which can be blocked or narrowed by a stopper 42.

An immersion nozzle 10 includes a pour-in part 11 having the shape of apipe and with plane end faces on the outlet side is fastened at theoutside of the base of the casting vessel 41.

The pour-in part 11 is connected with the a substantially rectangularpour-out part 21. On the outlet side, the pour-out part 21 dips into amelt S in a mold 51.

The pour-out part 21 has broad sides 22, and narrow sides 23, shown onthe right-hand side of the drawing, and an end wall 27 at the junctionbetween the pour-in part 11 and pour-out part 21. At least the add apour-out part is formed of a material which is heatable by means ofenergy that can be supplied externally. For this purpose, the materialcan be a refractory material in which are embedded metallic elementswhich are heatable by means of electrical energy.

Further, a heating device 31 is guided substantially parallel to thebroad sides 22.

The broad sides 22 and the narrow sides 23 are guided so as to besubstantially parallel to one another and have a distance a relative toone another with respect to a distance b of the narrow sides 23 in themouth region of the immersion casting pipe such that a<1/35×b. Theright-hand side of the FIG. 1 shows a configuration of the pour-out part21 in which the narrow sides 23 spread in the direction of flow at anangle a of less than 7°.

FIG. 2 is a perspective view of a pour-out part 21 whose broad sidesopen conically opposite to the direction of flow at the head end untilreaching an inner width K. This inner width K is in a relationship tothe outer diameter R of the round pour-in part 11 such that K/R=0.9-1.2.As is shown in the diagram, a square with edge length K extends in thecenter, on which the end face 12 of the tubular pour-in part 11 can beplaced or can even inserted through an opening of suitable size. The endwall 27 can be formed so as to narrow conically proceeding from edges K.

In an open section, FIG. 2 shows the free cross-sectional area of thepour-out part A_(E) which is calculated from the distance a between thebroad sides multiplied by the distance 6 between the narrow sides. Thecross-sectional area 22_(R) of the pour-in part 11 is in a relationshipto the rectangular free cross-sectional area A_(E) of the pour-out part21 such that A_(R) /A_(E) →1.7.

Also shown in the Figure is the length of the transition part 1, whoserelationship to the distance between the broad sides a is such thatI/A<1/4.

The overall length of the immersion casting pipe formed of the pour-inpart 11 and the pour-out part 21 is designated by L.

FIG. 3 shows of an immersion nozzle in which the pour-out part has aroof-shaped head end 24 of which fits into a slot 14 of the pour-in part11 at the head end in the central region. A head 25 of the pour-out part21 has an end wall 27 which opens in a roof-shaped manner from thepour-in part in the conveying direction to the edge of the broad sides22.

The slot 14 of the pour-in part 11 or of the roof shaped head end 24 ofthe pour-out part 21 corresponding to the slot 14 has a length l.

FIG. 2 shows a detail of the mouth region 13 of the pour-in part 11. Theslot 14 in the pour-in part into which the roof-shaped head end 24 fitsis shown from the top. A tongue 29 which fits into a groove 19 of thepour-in part 11 is provided at the part 24. The arrangement of thegroove 19 tongue 29 enable the pour-in part 11 and 21 pour-out parts toslide together horizontally; during operation, however, the pour-outpart 21 is prevented from falling out of the slot 14 of the pour-in part11.

The mouth region 13 of the tubular pour-in part 11 can be closed by adeflector element 16 which is arranged either vertically to the flowdirection of the liquid metal or has a flattened portion 15 as is shownon the right-hand side of the Figure.

FIG. 5 shows an immersion nozzle with a pour-out part 21 which isfastened at the casting vessel 41 completely independent from thepour-in part 11.

The pour-in part 11 which is arranged directly below the outlet opening43 of the casting vessel 41 is enclosed by an insert 28 in the castingspace G_(E) of the pour-out part 21. The insert 28 is shaped such thatthe flow of melt exiting the tubular pour-in part 11 is guided in asuitable manner without whirling.

The narrow sides are shown in figure. The pour-in part 11 has deflectorelements 16 in the mouth region 13 which narrow conically in thedirection of flow in the right-hand side of the picture, for example,through inserts 28, and which close the projecting portion of thepour-in part 11. This configuration the metal melt, of deflector element16 enable (not shown) which has a round cross section after exiting theoutlet opening 43, to be compelled along the shortest possible path toform a metal flow having a rectangular cross-sectional area with a largeratio of narrow sides to broad sides.

What is claimed is:
 1. An immersion nozzle for transferring melt from acasting vessel to a rectangular mold for the continuous casting of thinslabs of metal, comprising:a pour-in part comprising a pipe having acircular cross-section, a pour-in part input end fastened to a bottom ofthe casting vessel, and a pour-in part output end; a transition partconnected to said pour-in part output end; a pour-out part connected tosaid transition part such that the melt flows downwardly through saidtransition part to said pour-out part and said pour-out part having amouth which is suspended in the melt in the rectangular mold, said mouthbeing substantially rectangular in cross-section, said pour-out partcomprising planar-surface wall elements including a pair of parallelbroad sides and a pair of parallel narrow sides; said pour-in part andsaid pour-out part having a constant wall thickness; and a ratio of anarea A_(R) of said circular cross-section of said pour-in part to anarea A_(E) of said rectangular cross-section of said mouth of saidpour-out part being A_(R) /A_(E) ≦1.7.
 2. The immersion nozzle of claim1, wherein said pair of substantially parallel broad sides are separatedby a first distance (a), said pair of narrow sides are separated by asecond distance (b) at said mouth of said pour-out part, and said firstdistance (a) being related to said second distance (b) by a<1/35 b. 3.The immersion nozzle of claim 2, wherein said pair of narrow sidesspread apart toward said mouth of said pour-out part at an angle α<7°.4. The immersion nozzle of claim 2, wherein said transition part betweensaid pour-in part output end and said pour-out part planar surface wallelements has a length (l) defined by l/a<1/4.
 5. The immersion nozzle ofclaim 4, wherein said pour-in part output end includes a slot and saidtransition part comprises an extension of said planar surface wallelements engageable with said slot.
 6. The immersion nozzle of claim 5,wherein said extension comprises a roof-shaped head comprisingroof-shaped sides extending conically from a top of said slot to saidpair of narrow sides.
 7. The immersion nozzle of claim 5, wherein saidpour-in part output end comprises a flattened portion from a top of saidslot to outer edges of said broad sides operatively guiding said melttoward said pour-out part.
 8. The immersion nozzle of claim 4, whereinsaid transition part comprises extensions from said pair of broad sidesopening conically from a top of said pair of broad sides to said pour-inpart output end whereat said extensions are separated by a width (K)related to an outer diameter (R) of said pour-in part such that K/R ision the range of about 0.9 to 1.2.
 9. The immersion nozzle of claim 8,wherein said transition part further comprises roof-shaped sidesconnecting said pour-in part output end, an outer edge at a top of eachof said pair of narrow sides, and said extensions, wherein each of saidpair of roof-shaped sides has a width (K) at said pour-in part outputend and a width equal to said first distance (a) where said each one ofsaid pair of roof shaped sides meets said outer edge.
 10. The immersionnozzle of claim 4, wherein said pour-in part output end comprises agroove and said pour-out part comprises a tongue for operativeengagement with said groove for connecting said pour-in part to saidoutput part.
 11. The immersion nozzle of claim 5, wherein said pour-outpart comprises a length (L) substantially equal to a total length ofsaid immersion nozzle, said pour-in part being in loose contact withsaid pour-out part and said immersion nozzle comprising inserts whichdefine a casting space within said pour-in part and said pour-out part.12. The immersion nozzle of claim 11, wherein said inserts comprise afirst insert that encloses said pour-out part and a second insert insaid mouth of said pour-in part operatively narrowing a passage in saidpour-in part toward said pour-in part output end for minimizing awhirling of said melt in said immersion nozzle.
 13. The immersion nozzleof claim 1, wherein said pour-in part output end comprises a deflector.14. The immersion nozzle of claim 1, wherein said material comprises arefractory material having embedded metallic elements heatable byelectrical energy.